Grooving operations are typically performed by a cutting insert retained in an insert pocket located between upper and lower jaws of a tool holder. In some applications, the tool holder may be a relatively narrow holder blade, as shown for example in U.S. Pat. No. 4,357,123. In other applications the tool holder may have a relatively narrow holder blade-type forward portion, where the insert is retained, and a rear part of larger dimensions, as shown for example in U.S. Pat. No. 5,795,109. In some applications, the tool holder may be disc shaped, as shown for example in U.S. Pat. No. 5,820,309.
One of the problems with many of the tool holders of the types mentioned above and also of other types of tools holders is that the cutting inserts retained in the tool holders may become dislodged from their designed position due to outward or inward movement of the cutting insert. This may happen, for example, during slotting operations when attempting to withdraw the holder blade from a work piece. In some cases the cutting insert can be completely pulled out of the holder blade and become embedded in the work piece. Another example is with rotary slot-cutting tools where the cutting insert can even fly out of the insert pocket under the influence of centrifugal forces, a situation that can be particularly dangerous when operating at high speeds.
In U.S. Pat. No. 4,938,640 there is illustrated a metal cutting tool in which a cutting insert is clamped in a seat of a tool holder defined between oppositely facing clamping surfaces of clamping jaws of the tool holder. The lower clamping surface is provided with an arched projection which is adapted to fit in an arched recess formed in a base surface of the cutting insert, thereby providing a mechanism for preventing inward and outward displacement of the cutting insert. However, the seat of the tool holder cannot seat double ended cutting inserts. Moreover, even if one would attempt to locate a double ended cutting insert in the seat, the clamping jaws would have to be forced apart sufficiently to enable the insertion of the non-operative cutting end of the cutting insert into the seat since the free end of the upper clamping jaw is located directly opposite the projection, thereby minimizing the distance between the upper and lower clamping jaws at the forward end of the seat. Furthermore, with the free end of the upper clamping jaw located directly opposite the projection, the cutting portion of the cutting insert has to be positioned outside of the seat to distance the upper clamping edge from the cutting edges of the cutting insert, otherwise the chips removed from the workpiece would damage the upper clamping edge. A consequence of the cutting portion of the cutting insert being positioned outside of the seat is that it has no support from below.
Additionally, the arched projection and arched recess are not optimized for maximum prevention of inward and outward displacement of the cutting insert since no angles are given for the sloping surfaces of the arched protrusion and the arched recess. The arched protrusion and the arched recess are simply designed so that the projection will fit into the arched recess. Additionally, the clamping surface of the lower jaw comprises a simple keying rib extending rearwardly from the arched protrusion, whereby the stability of the insert is not uniquely determined.